Torsional dampers are well known devices that reduce torque fluctuations. Torsional dampers can be used to transmit torque between components inside the primary powerflow, to reduce vibrations caused by changes in rotational speed. Torsional dampers can also be used to connect a member subjected to a torsional load to a secondary inertia outside the primary powerflow, in which case they are sometimes referred to as absorbers.
Torsional dampers and absorbers are often used in automotive applications. For example, dual mass flywheels include a torsional damper, and are an example of a torsional damper assembly.
In its simplest form, a flywheel is simply a disc of significant mass that has a high moment of inertia. One function of the flywheel is to resist changes in rotational speed. In automobile powertrains, a flywheel is connected to the crankshaft of an internal combustion engine. Thus, in an internal combustion engine, the flywheel resists acceleration and deceleration of the crankshaft. This resistance to acceleration and deceleration reduces fluctuations in the rotational speed of the crankshaft that would otherwise be caused by linear reciprocal motion of the pistons. Without the flywheel, fluctuations in rotational speed in the crankshaft would cause potentially severe vibrations.
A dual mass flywheel includes two separate flywheel parts that are connected to one another by a torsional damper. The torsional damper connects the two flywheel parts such that relative rotation between them is allowed along the axis of rotation of the flywheel, with the torsional damper resisting relative rotation of the two flywheel parts and urging them to a rotationally neutral position.